Thermal performance, parametric analysis, and multi-objective optimization of a direct-expansion solar-assisted heat pump water heater using NSGA-II and decision makings

By Yan Cao, Leonardus W. W. Mihardjo, Towhid Parikhani. 2020

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Abstract This paper aims to develop a thermodynamic model and a multi-objective optimization for the thermal performance of a direct-expansion solar-assisted heat pump water heater. In the current investigation, the heat pump design parameters such as the solar collector area, compressor speed, length and outside diameter of the coil in the condenser, fin thickness, and collector plate conductivity are chosen as decision variables. A parametric study is conducted to identify how various input factors may affect the DX-SAHPWH system. A multi-objective non-dominated sorting genetic algorithm (NSGA–II) is employed to obtain the optimal solutions of design parameters, where the coefficient of performance (COP) and the solar collector efficiency (SCE) are taken as two fitness functions. The achieved optimum solutions from the bi-criteria optimization process is given as Pareto frontier. The ultimate optimal solution from available solutions on the Pareto optimal curve is selected using decision-makings, such as LINMAP, TOPSIS, and Shannon’s Entropy methods. In addition, single-objective optimization is performed for each objective function in order to compare the results with the optimum solutions achieved by the bi-objective optimization as well as the performance measures of the base-case system to identify the behavior of the objective functions. The comparisons of single and bi-objective optimization results illustrate that bi-objective optimization method yields more proper results than single ones, mainly because of the lower deviation index from the ideal solution. The results of bi-objective optimization show 8.76% diminution in the SCE compared to the initial test case while the COP increases close to 91.53% that makes the optimal solution more desirable respect to the single ones.

Subfields: Mechanical Engineering, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/b97f21671a9316cea74997b6d43b9d109a9dfd57